Both Freelancer and the Cutlass seem to have about the same cargo space. Assuming those numbers are accurate. Besides those, the Hull B or C seem to be very nice options.
The Lancer carries almost double the cargo of the Cutty, and almost 4X as much in the Max version. It is important to note that if you are doing short hauls in safe space, you really do want the largest freighter you can buy since that will generate your profits.
The Hull series should be the best choice for straight hauling in safe space, but I do like to remind people that the Starfarer is a great transport. I especially like the G. It carries more standard cargo than the Lancers, plus all that gaseous cargo including gathering and refining. Also the Starfarers can refuel short range fighters. People most often ignore the range issue and it will become extremely important to all transport pilots. Range is not a game issue yet, but it will be, and the SF's can refuel short range fighters--at least the ones with a fuel probe like the Tana. That means it can support short range escorts, and short range fighters generally have better dog-fighting capabilities than long range fighters. If it turns out a Starfarer can refuel Hornets, I would recommend that combo for a thousand missions. That is the kind of operation 2-4 players can support themselves with and have enough variety to never get bored.